Participation of serotonin (hereinafter referred to as 5-HT) in antidepressive action has been reported [Norio Ogawa (ed.), Shinnonoreseputa, Sekai Hoken Tsushinsha (1991, etc.)], and studies have been directed to 5-HT reuptake inhibition or action on 5-HT receptors.
Tricyclic compounds such as Amitriptyline are widely used clinically as antidepressants. Although Amitriptyline exhibits a 5-HT reuptake inhibitory activity or a 5-HT.sub.2 receptor antagonistic activity, it additionally has a noradrenaline reuptake inhibitory activity and an anticholine activity and exhibits non-selective action and is therefore considered to cause side effects upon the cardiovascular system (e.g., palpitation), thirst, urinary retention, etc. Therefore, drugs which selectively inhibit 5-HT reuptake or selectively act on 5-HT.sub.2 receptors are expected to have reduced side effects. Drugs selectively inhibitory on 5-HT reincorporation which have been clinically used include, for example, Fluoxetine. However, it has been reported that Fluoxetine induces anxiety or insomnia during the course of therapy [Physician's Desk Reference, Medical Economics Company, Oradell, N.J. (1990)].
Drugs which selectively antagonize for 5-HT.sub.2 receptors include, for example, Mianserin which is known as an antidepressive.
In the latest various studies, a compound having a selective 5-HT reuptake inhibitory activity together with a selective 5-HT.sub.2 receptor antagonistic activity is eagerly awaited [Cell Biology to Pharmacology and Therapeutics, 488-504 (1990 ), Psychopathology, 22 (suppl. 1 ), 22-36 (1989), J. Clin. Psychiatry, 52, 34-38 (1991), Psychopharmacol. Bull., 26, 168-171 (1990), and Br. J. Pharmacolo., 100, 793-799 (1990)].
Drugs having both of a 5-HT reuptake inhibitory activity and a 5-HT.sub.2 receptor antagonistic activity include, for example, Trazodone. However, the 5-HT reuptake inhibitory activity of Trazodone is very weak, and it was reported that the antidepressive activity and antianxiety activity of Trazodone are based on its antagonism for 5-HT.sub.2 receptors. [Marek G. J., et al., Psychopharmacology, 109, 2-11 (1992)]. Further, in addition to the above two activities Trazodone also exhibits affinity to .alpha..sub.1 receptors and therefore causes sides effects based thereon.
JP-A-46-7333 (the term "JP-A" means an "unexamined published Japanese patent application") discloses 2-[[(4-indanyl)oxy] methyl]morpholine, and JP-A-52-83773 discloses 2-[[(7-indenyl)oxy]methyl]morpholine. However, these compounds have no substituent on the indanyloxy group or indenyloxy group thereof.